Autoclaved aerated concrete fire sentry encasements

ABSTRACT

A fireproofing method for structural building construction members is disclosed. The method includes encasing a portion of each building construction member with autoclaved aerated concrete (AAC) elements profiled to surround exterior profiles of the portion of the each building construction member.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Serial No. 60/381,944, filed May 17, 2002, which is hereby incorporated by reference.

BACKGROUND

[0002] This invention relates generally to fire shield enclosures or encasements or of pre-cast autoclaved aerated concrete, and field sprayed or formed, poured or cast aerated concrete surrounding structural steel, structural steel reinforced concrete or structural supports of metal, wood, or concrete arranged or erected for structural support of buildings. The primary purpose of such products is protection of properties such as physical strength of such structural members or supports which become engulfed, surrounded or exposed to high temperatures due to fires or other heat sources approaching or exceeding 2000 degrees Fahrenheit.

[0003] A Swedish architect first developed the basic product of aerated concrete or autoclaved aerated concrete (AAC) in Europe. The architect came upon the material by accident in 1917 while observing aluminum hulled ships being filled with normal concrete for ballast. The concrete expanded several times greater than its original volume when exposed to the metal aluminum. Several experimental formulations later produced a viable material usable in building construction and other applications.

[0004] AAC displays important properties. First, blocks of AAC may easily be cut into desired shapes and sizes. Second, AAC is lightweight compared to normal concrete. For example, typical AAC weighs one-fourth to one-fifth the weight of normal concrete, which weighs in the range 130 to 145 lbs/ft. Third, AAC has extreme thermal properties. It displays no spalling of material when exposed to temperatures at or approaching 2000 degrees Fahrenheit. Fourth, AAC is an inorganic material resistant to weather decay and pest attack.

[0005] AAC is typically formed as a blend of sand or fly ash, lime, Portland cement, water, and an expansion agent of aluminum powder or paste. The mixture is usually cast into large molds and allowed to expand to a volume greater than the original semi-fluid mass. The expanded mass is sliced to desired dimensions into units of block or panels. The processed panels or blocks are then placed into large pressurized chambers called autoclaves to complete the curing or hardening of the finished product. The block or panel pieces are usually cured for 8-12 hours at 12-13 atmospheric pressures at 360-385 degrees Fahrenheit.

[0006] Aerated concrete is produced in similar shapes or fashions like autoclaved aerated concrete. However, aerated concrete product is allowed to air cure in normal single atmospheric pressures and ambient temperatures. The process for achieving maximum strengths of product (blocks and shapes) takes longer. Typical curing time for aerated concrete is 7-28 days versus 20-24 hours for autoclaved aerated concrete.

[0007] AAC has been produced in a variety of shapes, sizes and densities by several recognized name brand manufacturers and licensed manufacturers. These include YTONG Holding AG, Munich, Germany, Josef Hebel GmbH & Co., Memmingen, Germany, and Durox Ltd., Linford, UK. These manufacturers make standard elements for construction of walls, roofs and floors.

[0008] In general, AAC has been limited in use for building solid block walls, roof structures and flooring. The thermal properties of AAC may have other uses, as well.

[0009] In particular, many buildings have a wooden frame or skeleton of steel or other materials. Modem building fire codes require fireproof material be applied to steel construction members. Currently, a spray-on concrete fireproofing material is applied to girders and other portions of steel building skeletons. While effective, this spray-on material is notorious for readily cracking, chipping and simply falling off. Examples are well known of the material breaking off during a mechanical repair or modification. In the event of a failure such as this, the fireproofing of the entire building is at risk. A small chip or crack can expand until entire beams or sections of the skeleton are exposed.

[0010] Accordingly, there is a need for improved fireproofing systems, methods and materials for structural supports for buildings and other structures.

BRIEF SUMMARY

[0011] By way of introduction only, the present embodiments provide a unique system of designed and profiled manufactured autoclaved aerated concrete (AAC) components or elements to wrap or encase structural supports or columns made primarily of steel. The AAC components or elements conform to the exterior profiles of steel I beams, columns, angles, channels or various steel superstructures. The resultant system forms a protective shield resistant to high heat experienced in some fuel type fires.

[0012] The disclosed method and apparatus provide a complete system of pre-cast or modified AAC elements or aerated components designed to encase or surround structural or nonstructural supports or members of wood, steel, concrete or composites thereof. These encasements are pre-cast in a variety of sizes, shapes and densities, or are field sprayed or formed, poured or cast on site to conform to the physical dimensional symmetric or asymmetric profiles, vertically or horizontally, of structural or non-structural supports or members.

[0013] The primary purpose is to protect or shield the physical strength properties of these structural or non-structural members, supports or structures when they are engulfed, exposed, surrounded by high temperatures approaching or exceeding 2000 degrees Fahrenheit for extended periods such as 2 to 4 hours.

[0014] Other features and advantages of the disclosed embodiments, as well as alternative embodiments to which the concepts disclosed herein may be extended, will be evident from the following description. The foregoing discussion of illustrative embodiments of the invention has been provided only by way of introduction. Nothing in this section should be taken as a limitation on the following claims, which define the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 illustrates a profiled a cylindrical structural steel support member encased by autoclaved aerated concrete (AAC);

[0016]FIG. 2 illustrates a steel I beam encased by profiled AAC;

[0017]FIG. 3 illustrates a steel square tube encased by profiled AAC;

[0018]FIG. 4 illustrates a steel angle iron encased by profiled AAC;

[0019]FIG. 5 illustrates spray application of aerated concrete on irregular steel surfaces and cavities;

[0020]FIG. 6 illustrates high heat and the protection of physical characteristics of steel structure afforded by AAC encasements; and

[0021]FIG. 7 illustrates use of a mechanical spiral fastener of stainless steel anchoring irregular asymmetric pieces of AAC;

[0022]FIG. 8 is a cross section view of a first embodiment of AAC encasements used in conjunction with an I-beam supporting a concrete floor;

[0023]FIG. 9 is a cross section view of a second embodiment of AAC encasements used in conjunction with an I-beam supporting a concrete floor;

[0024]FIG. 10 is a cross section view of a first embodiment of AAC encasements used in conjunction with an I-beam support pillar;

[0025]FIG. 11 is a cross section view of a second embodiment of AAC encasements used in conjunction with an I-beam support pillar;

[0026]FIG. 12 is a cross section view of a third embodiment of AAC encasements used in conjunction with an I-beam support pillar;

[0027]FIG. 13 is a cross section view of AAC encasements used in conjunction with a support pillar; and

[0028]FIG. 14 is a cross section view of AAC encasements used in conjunction with a support pillar.

DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED EMBODIMENTS

[0029] Referring now to the drawing, FIG. 1 includes an isometric view in FIG. 1(a) and a top view in FIG. 1(b) of a fireproofed support beam 100. The support beam 100 includes a building construction member 102 and fireproofing 104 formed of a plurality of pre-formed, autoclaved aerated concrete (AAC) elements 106, 108,110, 112. In the illustrated embodiment, the AAC elements 106, 108,110, 112 surround a standard cylindrical steel member 102. In alternative embodiments, the building construction member 102 may be conventional concrete, wood or any other material having insufficient fire retardant properties.

[0030] In the embodiment of FIG. 1, the AAC elements 106, 108,110, 112 extend along the entire length of the member 102 so as to substantially encase the member 102. That is, none of the member 102 is exposed to the air and to elevated ambient temperatures. The fireproofing 104 thermally insulates the member 104. This encasement relation between the AAC elements 106, 108,110, 112 and the building construction member 102 is the preferred embodiment and provides maximum fireproofing, or resistance to elevated temperatures, for the member 102.

[0031] The AAC elements 106, 108, 110, 112 are profiled to surround the exterior profile 114 of the building construction member 102. Thus, as is most clearly illustrated in FIG. 1(b), the fireproofing for the cylindrical member 102 is annular and comprises four substantially equally sized and shaped elements 106, 108, 110, 112. In other embodiments, the shapes and profiles and number of the fireproofing elements may be varied. For example, the fireproofing 104 may include only two elements, each substantially one-half of an annulus to encase the member 102. Other numbers, such as 3, 6 or 8 elements may be used.

[0032] In the illustrated embodiment, the exterior profile 114 of the member 102 is cylindrical. In other embodiments, to be described below in conjunction with FIGS. 2-4, the member 102 may have any type of exterior profile. Further, in the embodiment of FIG. 1, the exterior profile 114 of the member 102 is substantially regular along the length of the member. In many applications, the exterior profile of the member 102 will be irregular. Examples of this will be described below. To accommodate an irregular profile, the respective elements 106, 108, 110, 112 may be sized or shaped appropriately. The result may be a patchwork, mosaic or tessellated structure.

[0033] Thus, the AAC elements are profiled to surround the exterior profile 114 of the building construction member 102. This profiling occurs in the aggregate, with each AAC element contributing a portion of the inner profile 116 of the fireproofing 104 so that the inner profile 116 substantially matches the exterior profile 114 of the of the building construction member 102. The exterior profile 118 of the fireproofing 104 may have any profile. In the illustrated embodiment, the exterior profile 118 of the fireproofing is cylindrical and matches the exterior profile of the encased building construction member 102. In alternative embodiments, the exterior profile 118 of the fireproofing may have a completely different profile, or may be irregularly shaped. The exterior profile may be chosen to meet design and performance requirements of other portions of the building under construction.

[0034] Further, each element 106, 108, 110, 112 has a length to substantially match the length of the member 102. In alternative embodiments, respective elements may have any suitable length or the lengths of the elements may be varied so as to provide an interlocking pattern of elements where the advantages of such a pattern may be desired. The elements 106, 108, 110, 112 form an assembly which is constructed in various profiled AAC pieces or elements to form a complete protective shield or wrap around the steel or other member 102.

[0035] The AAC elements 106, 108, 110, 112 are formed of a material that is a blend of sand or fly ash, lime, Portland cement and aluminum expansion agents. It is well within the purview of those ordinarily skilled in the art to select or vary the exact combination of these materials and others to meet particular design goals.

[0036] The elements 106, 108, 110, 112 are joined together and to the member with a thin bed mortar 120 designed for use with autoclaved aerated concrete as per standards established by the American Society for Testing Materials (ASTM). In one embodiment, the mortar 120 is 1450 PSI thin bed mortar according to American National Standards Institute (ANSI) standard A118.4 of Latex/Portland cement. In some embodiments, the mortar 120 may be modified with refractory fire clay. The AAC material is fire rated per standards established, for example, by Underwriter's Laboratory, Inc. (U.L.) at a fire rating approximately equal to one hour per inch of wall material. On example of such a standard is U.L. design X901. Thus, the fire resistance of the fireproofing 104 can be tailored by varying the thickness of the fireproofing. The thickness and the materials used in the AAC elements are chosen to meet the desired fire resistance standard.

[0037] The mortar in one embodiment is a thin bed type made to present ASTM standards for AAC to join various AAC elements. The AAC elements of the disclosed system are intended for high temperature exposure. In this embodiment, an addition of refractory fire clay per uniform Brick Institute of America and ASTM is added at a minimal rate of 8% of the AAC Thin Bed Mortar manufacturer's printed bag weight, not to exceed 10% of the printed bag weight. The purpose of the refractory is to provide margin of safety in preserving the structural joining of the AAC Elements when exposed to high heat fires.

[0038] The assembly in its present configuration is rated at 2-4 hours dependent upon the wall thickness of the profiled AAC element. Mechanical fasteners of fire rated quality may be used in shoring up additionally attached exterior pieces as will be described below. For example, the cylindrical member 102 surrounded by the cylindrical fireproofing 104 may be fastened by circular straps at one or more positions along its length. The straps can be tightened to the exterior profile 118 of the fireproofing 104 using an appropriate tool. Alternatively, a fastener can be driven through the AAC elements to attach to the member 102 or driven through adjacent members. The straps or other fasteners may be left permanently or may be removed after the mortar 120 has cured.

[0039] The individual AAC elements may be profiled in any suitable manner. For example, the elements may be cast by pouring a fluid mixture of aerated concrete into a mold and allowing the mixture to cure. After removal from the mold, the elements may be placed into an autoclave to complete the hardening process. Before or after autoclaving, the concrete pieces may be further shaped by hand or by tools. The concrete can easily be cut or ground into any shape required to match the exterior profile of a building component. The entire process can be performed at a concrete plant or done on site. In one process, aerated concrete blocks of standard size and shape are formed and subsequently cut to size before installation. Most of a standard building construction member can be covered with pre-cast, standard sized and shaped blocks. Some portions, such as ends or joint of construction members, are then encased by piecing smaller blocks together. The smaller blocks or portions of larger blocks may be shaped using appropriate tools to match an exterior profile of a portion of a building construction member. In some, cases, spray-on aerated concrete may be used to fill voids, as will be described below in conjunction with FIG. 5.

[0040]FIGS. 2, 3, 4 and 5 illustrate how AAC elements may be configured to match up and wrap or encase various external profiles of steel or other building construction member. These drawing figures illustrate the various profile shapes the AAC elements will take to cover a broad spectrum of structural building construction member shapes.

[0041] In FIG. 2, the building construction member 202 is in the form of a steel I-beam. FIG. 2 shows a top view, FIG. 2(a), and a cross-sectional view, FIG. 2(b), taken along line 2-2′ in FIG. 2(a). In the top view of FIG. 2(a), the construction member 202 clearly has an I-shaped cross section.

[0042] As in FIG. 2, the I-beam building construction member 202 is encased in fireproofing 204. The fireproofing 204 includes a plurality of pre-formed, autoclaved aerated concrete (AAC) elements which are profiled to surround the exterior profile 226 of the building construction member 202.

[0043] In the embodiment of FIG. 2, the AAC elements are segmented along the length of the member 202. The top portion 226 of the I-beam in encased in four AAC elements 206, 208,210,212. Each element 206,208,210, 212 is generally U-shaped having a central slot 228 sized and shaped to match one portion of the I-shaped beam. The U-shaped element 206, 208, 210, 212 has two legs. One leg is shaped to match part of the central portion of the I-beam. The other leg is shaped to define the exterior perimeter 232 of the fireproofing 204 and has a leg end shaped to mate with the leg end of an opposing U-shaped element. In the embodiment of FIG. 2, the exterior perimeter 232 of the fireproofing 204 is substantially square with rounded corners. Any other suitable perimeter shape, regular or irregular, could be chosen to meet specific design and performance goals. Other shapes will be described below in conjunction with FIGS. 8-12.

[0044] Below the AAC elements 206, 208, 210, 212 at the top portion 226 of the member 202 are a next segment of elements. In the cross sectional view of FIG. 2(b), elements 214, 216 are visible. A similar pair of elements mates with or matches these elements to encase this portion 236 of the I-beam. Similarly, below the elements 214, 216, elements 218 and 220 encase a portion 238 of the I-beam. Finally, the bottom portion 240 of the I-beam is encased in AAC elements including elements 222, 224.

[0045] In combination, then, the elements 206, 208, 210, 212, 214, 216, 218, 220, 222, 224 match in surrounding, joining relationship the exterior profile of the I-beam, building construction member 202. Each element individually is profiled to match an exterior profile of a portion of the building construction member 202.

[0046] The AAC elements are joined to the I-beam in any suitable manner. In the preferred embodiment, a fire refractory clay modified thin bed mortar is applied to the steel I-beam and the AAC elements are positioned in the mortar. Additional mortar may be filled between the AAC elements to ensure no gaps in the fireproofing 204. Any suitable mortar having the requisite thermal and mechanical properties may be used. In addition or in the alternative, fasteners may be used to mechanically fasten the AAC elements to the I-beam or other building construction member.

[0047] In FIG. 3, a building construction member 302 is in the form of a tubular steel beam. FIG. 3 shows a top view, FIG. 3(a), and a cross-sectional view, FIG. 3(b), taken along line 3-3′ in FIG. 3(a). In the top view of FIG. 3(a), the construction member 302 clearly has tubular cross section.

[0048] As in FIGS. 1 and 2, the tubular building construction member 302 is encased in fireproofing 304. The fireproofing 304 includes a plurality of preformed, autoclaved aerated concrete (AAC) elements which are profiled to surround the exterior profile of the building construction member 302.

[0049] In the embodiment of FIG. 3, the AAC elements are segmented along the length of the member 302. A top portion 306 of the member 302 is encased in AAC elements 308, 310, 312, 314. A central portion 316 of the member 302 is encased in AAC elements including elements 316, 318. A similar pair of elements matches the elements 316, 318 to encase the member 302. Finally, the bottom portion 320 of the member 302 is encased in AAC elements including elements 322, 324 and a matching pair not visible in the drawing figure.

[0050] In the embodiment of FIG. 3, the AAC elements are all regularly shaped and sized and positioned along the tubular beam 302. This regular pattern may be preferable in some applications since a common size and shape of AAC block may be repeatedly manufactured and installed. Using mass production and automating the installation, the manufacturing cost and time are reduced or minimized for installing the fireproofing 204. This is especially true when constructing a large building with many identical I-beams or other members, such as a high-rise office building.

[0051]FIG. 4 illustrates an angle iron 402 encased in fireproofing 402. The fireproofing includes a plurality of AAC elements. FIG. 4(a) is a top view and FIG. 4(b) is a cross sectional view taken along line 4-4′. In FIG. 4(a), AAC elements 406, 408 are visible. In the cross sectional view of FIG. 4(b), it can be seen that AAC elements 406, 408 encase the top portion of the angle iron 402. Further, the fireproofing 404 includes AAC elements 410, 412 which encase the central portion of the angle iron 402 and AAC elements 414, 416 which encase the bottom portion of the angle iron 402.

[0052] The AAC elements may be shaped in any suitable manner to encase the building construction member formed by the angle iron 402. In the top view of FIG. 4(a), it can be seen that the AAC element 406 is mortared to the broad face 420 of the angle iron 402. Similarly, the AAC element 408 is mortared to sides 422, 424 of the angle iron 402 and the reverse side 426 of the broad face 420 of the angle iron. This segmentation of the AAC elements provides large surface areas for receiving mortar to securely retain the AAC elements to the building construction member. The encasement of the angle iron 402 may be segmented among two or more AAC elements in any suitable fashion.

[0053]FIG. 5 illustrates the use of a wet aerated concrete mix to fill unusual voids or profiles of a building construction member. In FIG. 5, an oddly shaped building construction member 502 is substantially encased by fireproofing 504 including AAC elements 506, 508. However, some voids remain in the fireproofing 504. The voids or cavities in the exterior profiles of the building construction member 502 may occur because of the odd shape, which can not be completely encased by the AAC elements 506, 508. Alternatively, the voids or cavities might occur which are too small to readily fill with another AAC element.

[0054] Accordingly, to complete the protective fire shield provided by the fireproofing, to provide a minimum fire rating of 2 hours or preferably a 4 hour rating for the member 502, a spray-applied mixture 510 including aerated concrete is applied to the fireproofing 504. In one embodiment, voids are filled with the aid of a plaster pump gun 512, which mixes all the ingredients required to make the aerated concrete needed to complete the application process. Other methods of applying the aerated concrete mixture may be used as well, such as troweling the mixture into the void or portions of the void. The spray-applied mixture 510 fills one or more cavities around the exterior profile of the building construction member not covered by the AAC elements 506, 508. The mixture 510 adheres to the building construction member 502 and to the AAC elements 506, 508 in the void. As the aerated concrete mixture 510 dries and cures, it expands to substantially completely fill the void and complete the protective fire shield.

[0055]FIG. 6 illustrates a steel building construction member 604 encased in fireproofing including one or more autoclaved aerated concrete (AAC) or aerated concrete (AC) elements. FIG. 6 illustrates qualitatively the temperatures of the exterior portion of AAC profiled elements 602 encasing a cylindrical steel building construction member 604 after a period of two hours of exposure to a high fire of approximately 2000 degrees Fahrenheit.

[0056] The internal encasement temperatures of the internal face 606 of the AAC elements 602, adjacent to the steel building construction member 604, is illustrated as a general range and distribution over the length of the steel building construction member 604. The range of internal temperature is approximately 140-170 degrees Fahrenheit. The exact temperature at any point within the fireproofing formed by the AAC elements 606 will depend on physical properties such as density of AAC or aerated concrete (AC) and will vary with raw materials, curing times and methods used in forming and assembling the AAC elements. The type of steel used in the building construction member 604 will also affect specific temperatures gained by conducted heat from AAC elements 602.

[0057]FIG. 7 illustrates a structural steel building construction member 702 surrounded by fireproofing 704. The fireproofing 704 includes a plurality of autoclaved aerated concrete (AAC) elements 706 profiled to surround the exterior profile 708 of the building construction member 702. The fireproofing 704 includes mortar 710. The mortar 710 is configured for binding the AAC elements 706 to the exterior profile 708 of the building construction member 702. The mortar in this embodiment is fire refractory clay modified thin bed mortar. Other suitable mortars may be substituted.

[0058] In this embodiment, the fireproofing 704 further includes one or more fasteners 712 configured to retain the AAC elements when assembled with the building construction member 702. As illustrated in this exemplary embodiment, an ornamental AAC element 714 is added to the exterior 716 of the fireproofing by driving a fastener 718 through the ornamental AAC element 714 into another AAC element 718 of the fireproofing 704. In this example, the fastener 718 is a stainless steel spiral fastener driven by a power hammer drill. Other types of fasteners may be used as well. The technique may be used with all types of AAC or AC elements added to the fireproofing, not just ornamental elements. Also, the technique may be used to join the AAC elements 706 of the fireproofing to improve mechanical strength or rigidity.

[0059]FIG. 8 is a cross section view of a first embodiment of AAC encasements used in conjunction with an I-beam 802 supporting a concrete floor 804. The concrete floor 804 is a concrete slab or concrete over a metal deck. The I-beam 802 directly supports the floor 804 in this embodiment, but in other embodiments, there may be other components interposed with the beam 802. The I-beam 802 includes a web 806 and beams 808, 810.

[0060] AAC masonry blocks 812, 814 are applied around the beam 802 and joined together with a suitable material, such as an ANSI Al 18.4 Latex/Portland cement thin bed mortar at a join 816. In this embodiment, to retain the AAC block 812, 814 to the beam 802, studs 818 are welded to the web 806 of the beam 802. The AAC blocks 812, 814 are profiled to match the outer profile of the beam 802. The blocks 812, 814 are routed to define grooves 820, 822 to match the profile of the beams 808, 810, respectively. The blocks 812, 814 are drilled with holes to match the studs 818. The holes are packed solid with a grout to form a secure fitting. A suitable fire stop material 824 is positioned between the AAC blocks 812, 814 and the steel I-beam 802 as additional insulation.

[0061]FIG. 9 is a cross section view of a second embodiment of AAC encasements used in conjunction with an I-beam 802 supporting a concrete floor 804. The arrangement of FIG. 9 is similar to that of FIG. 8 and like reference numerals are used to designate like elements. In addition to the AAC blocks 812, 814, an additional AAC form block 902 is added to the arrangement of FIG. 9 to further increase the fire resistance of the AAC encasements. The thin bed mortar joint 816 joins the AAC blocks 814, 816 as in FIG. 8. In addition, a second thin bed mortar joint 904 is formed between the AAC form block 902 and the AAC blocks 812, 814.

[0062] The form block 902 serves to increase the fire resistance of the beam 802. The form block 902 adds additional thermal insulation, particularly in the area of the thin bed mortar joint 816, to reduce the likelihood of failure of the beam 802 due to heating from fire below the beam 802. The goal of fireproofing is to increase the time available for evacuation of personnel in a building such as a steel framed high rise. Addition of the form block 902 or other similar enhancements may achieve that goal.

[0063]FIG. 10 is a cross section view of a first embodiment of AAC encasements used in conjunction with an I-beam support pillar 1002. AAC blocks 1004, 1006, 1008, and 1010 are applied around the pillar 1002 and joined together with a thin bed mortar at joints such as join 1012. In the illustrated embodiment, the thin bed mortar used is prepared according to ANSI A118.4 using Latex/Portland cement. The AAC blocks 1004, 1006, 1008, 1010 are fabricated in accordance with U.L. design X901. In the embodiment of FIG. 10, the blocks 1004, 1006, 1008, and 1010 are all of generally uniform size and shape and are joined to define a channel containing the pillar 1002. Preferably, the AAC blocks 1004, 1006, 1008, and 1010 are held in place with stainless steel masonry spiral fasteners until the thin bed mortar reaches required strength. Further, the AAC masonry blocks may be attached to the steel pillar 1002 with CMU wire-type column clips, for example at 24 inch on-center spacing. Other mechanical schemes may be used to temporarily or permanently join the pillar 1002 and the AAC blocks 1004, 1006, 1008, and 1010.

[0064]FIG. 11 is a cross section view of a second embodiment of AAC encasements used in conjunction with an I-beam support pillar. In the embodiment of FIG. 11, AAC masonry blocks 1102 and 1104 are applied around a column or pillar 1002 and joined together with thin bed mortar of the type described herein. The thin bed mortar is applied at joints such as the joint 1106 between the blocks 1102 and 1104. In the embodiment of FIG. 11, the blocks 1102 and 1104 are profiled to generally match the profile of the beam 1002. Thus, the blocks 1102 and 1104 are routed to define grooves or channels 1108 shaped to match the beams and web of the pillar 1002. The space between the routed grooves 1108 and the beam 1002 may be filled with thin bed mortar or other material. As with the embodiment of FIG. 10, the AAC blocks 1102, and 1104 may be held in place with stainless steel masonry spiral fasteners until the thin bed mortar reaches required strength. Further, the AAC masonry blocks may be retained to the steel pillar 1002 with CMU wire-type column clips, for example at 24 inch on-center spacing. Other mechanical schemes may be used.

[0065]FIG. 12 is a cross section view of a third embodiment of AAC encasements used in conjunction with an I-beam support pillar 1002. The embodiment of FIG. 12 is generally similar to the embodiment of FIG. 11, in that the autoclaved aerated concrete blocks 1102 and 1104 are profiled to match the profile of the beam or pillar 1002. However, to enhance the resistance of the encasements to fire and to reduce the likelihood of damage to the pillar 1002, the embodiment further includes AAC form blocks 1202, and 1204. Thin bed mortar joints 1206, and 1208 are formed between the AAC form block 1202 &1204 and the AAC blocks 1102, 1104.

[0066] The form blocks 1204, 1206 serve to increase the fire resistance of the beam 1002. The form blocks 1204, 1206 add additional thermal insulation, particularly in the area of the thin bed mortar joint 1106, to reduce the likelihood of failure of the beam 1002 due to heating from fire below the beam 1002.

[0067]FIG. 13 is a cross section view of AAC encasements used in conjunction with a rectangular support pillar 1302. The pillar 1302 in this embodiment is a tubular steel column. In the embodiment of FIG. 12, AAC blocks 1304, 1306, 1308, and 1310 are applied around the pillar 1302 and joined together with a thin bed mortar, such as the 1450 PSI thin bed mortar in accordance with ANSI A118.4 of latex and Portland cement. The mortar forms joints such as the joint 1312. The blocks 1304, 1306, 1308, 1310 are all substantially identical but in other embodiments, may be customized or modified to meet particular design goals. The AAC blocks 1304, 1306, 1308, 1310 may be held in place with stainless steel masonry spiral fasteners until the thin bed mortar reaches required strength. Further, the AAC masonry blocks may be fastened to the steel pillar 1002 with CMU wire-type column clips, for example at 24 inch on-center spacing. Other mechanical schemes may be used.

[0068]FIG. 14 is a cross section view of AAC encasements used in conjunction with a support pillar 1302. In the embodiment of FIG. 14, a technique is illustrated for securing the AAC blocks 1304, 1306, 1308, 1310 to the pillar 1302. In particular, on each side of the pillar 1302, anchor slots 1312 are provided which engage with anchors 1314 nailed to the AAC blocks 1304, 1306, 1308, 1310. Securing the anchor slots 1312 to the pillar 1302 are suitable pins 1316 such as Hilti Enph2 or equal performance specification shot pins. The anchor slots 1314 in one embodiment are 22 gauge anchor slots, Burke Fleming or equivalent, preferably placed generally along the centerline of the pillar 1302 along each face of the pillar 1302. The anchors 1314 in this embodiment are 14 gauge galvanic anchors, one per face of the pillar 1302, for example on 24 inch centers along the length of the pillar 1302. In this embodiment, the AAC blocks 1304, 1306, 1308, 1310 are applied around the column 1302 and are joined together with 1450 PSI thin bed mortar of the type described herein. During assembly, the AAC blocks are held in place with stainless steel masonry spiral fasteners until the thin bed mortar has reached sufficient strength.

[0069] From the foregoing it can be seen that AAC encasements include a plurality of pre-cast autoclaved aerated concrete and on-site cast aerated concrete reinforced and non-reinforced components elements to encase, wrap or encapsulate steel or reinforced steel structural supports or columns. The plurality of components and elements comprise a system to provide a protective shield from high to extreme heat as generated from petroleum base fuel fires such as jet fuel, gasoline, diesel, or kerosene, or other fire sources approaching or exceeding 2000 degrees Fahrenheit.

[0070] The total system protects structural steel and other materials for a period between 2-4 hours, depending on encasement wall thickness. The protective fire shield formed by the AAC system greatly enhances physical ability of steel to carry heavy dead and live loads normally diminished in high heat fires. The protective shield of the discloded embodiments provide allows larger time windows for fire and rescue personnel to evacuate and control massive fires in high-rise, high population buildings constructed of steel support structures.

[0071] While a particular embodiment of the present invention has been shown and described, modifications may be made. It is therfore intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention. 

We claim:
 1. Fireproofing comprising: a plurality of pre-formed, autoclaved aerated concrete (AAC) elements profiled to surround the exterior profiles of building construction members.
 2. The fireproofing of claim 1 further comprising: one or more fasteners configured to retain the plurality of AAC elements when assembled with the building construction members.
 3. The fireproofing of claim 2 wherein the one or more fasteners comprise spiral fasteners configured to be driven into one or more AAC elements.
 4. The fireproofing of claim 1 further comprising mortar.
 5. The fireproofing of claim 4 wherein the mortar is configured for binding the plurality of AAC elements to the exterior profiles of the building construction members.
 6. The fireproofing of claim 4 wherein the mortar comprises a fire refractory clay modified thin bed mortar.
 7. The fireproofing of claim 1 wherein one or more AAC elements are pre-cast to match an exterior profile of a portion of a building construction member.
 8. The fireproofing of claim 7 wherein two or more AAC elements are pre-cast to match in surrounding, joining relationship the exterior profile of the portion of the building construction member.
 9. The fireproofing of claim 1 wherein one or more AAC elements are shaped to match an exterior profile of a portion of a building construction member.
 10. The fireproofing of claim 1 further comprising: a spray-applied mixture including aerated concrete.
 11. The fireproofing of claim 10 wherein the spray-applied mixture fills one or more cavities around the exterior profiles of the building construction members not covered by the AAC elements.
 12. A fireproofing method for structural building construction members, the method comprising: encasing at least a portion of each building construction member with autoclaved aerated concrete (AAC) elements profiled to surround exterior profiles of the portion of the each building construction member.
 13. The fireproofing method of claim 12 further comprising: spray-applying aerated concrete to fill voids between the AAC elements.
 14. The fireproofing method of claim 12 further comprising: spray-applying aerated concrete to encase joints between the AAC elements.
 15. The fireproofing method of claim 12 further comprising: mortaring the AAC elements to the portion of the each building construction member.
 16. The fireproofing method of claim 15 wherein mortaring the AAC elements comprises applying a refractory clay modified thin bed mortar suitable for use with autoclaved aerated concrete blocks.
 17. The fireproofing method of claim 12 further comprising: driving fasteners into two or more AAC elements to join the two or more AAC elements.
 18. The fireproofing method of claim 12 further comprising: driving fasteners into one or more AAC elements and one or more aerated concrete elements to join elements.
 19. The fireproofing method of claim 18 wherein driving fasteners comprises: driving spiral stainless steel fasteners with a rotary hammer drill. 